Pneumatic tire

Abstract

A pneumatic tire having a tread portion with a convex profile, a pair of axially spaced bead portions, and sidewall portions extending therebetween. The tread portion is provided with a pair of circumferentially extending continuous grooves defining groove edges with a combined width of more than 16% of the ground contacting width. The tire design reduces overall tire noise, especially air resonance without deteriorating tire performance on wet surfaces.

I claim: 
     
       1. A pneumatic tire comprising: a tread portion with tread edges, a pair of axially spaced bead portions, and sidewall portions extending therebetween,   said tread portion including a crown part and a pair of shoulder parts which collectively have a convex profile having s single radius or multiple radius,   said tread portion provided with two circumferential grooves divided by a center rib, each of the two circumferential grooves extending continuously in the circumferential direction of the tire and having a combined width of not more than 50% of the ground contacting width when the tire is mounted on a regular rim, inflated to a regular pressure and loaded with a regular load,   each of the circumferential grooves has an axially outer wall and an axially inner wall disposed perpendicular to a flat groove bottom,   the axially outer wall and the axially inner wall connecting to the groove bottom at rounded corners,   the rounded corner between the axially outer wall and the groove bottom having a radius of 1.5 to 3 times the radius of the rounded corner between the axially inner wall and the groove bottom.   
     
     
       2. The pneumatic tire according to claim 1, wherein the width of the center rib is in the range of from 5 to 15% of the ground contacting width. 
     
     
       3. The pneumatic tire according to claim 2, wherein one of said circumferential grooves is a zigzag shaped groove. 
     
     
       4. The pneumatic tire according to claim 1, wherein one of said circumferential grooves is a straight groove. 
     
     
       5. The pneumatic tire according to claim 1, wherein one of the two circumferential grooves is a straight groove, and the other circumferential groove is a zigzag groove. 
     
     
       6. The pneumatic tire according to claim 1, wherein the depth of each of the circumferential grooves is in the range of 4% to 8% of the ground contacting width. 
     
     
       7. The pneumatic tire according to claim 1, wherein the width of one of the circumferential grooves is more than 16% of the ground contacting width. 
     
     
       8. The pneumatic tire according to claim 1, wherein one of the circumferential grooves is of a width less than 8% of the ground contacting width. 
     
     
       9. The pneumatic tire according to claim 1, wherein the center rib extends continuously in the circumferential direction of the tire. 
     
     
       10. The pneumatic tire according to claim 9, further comprising a center rib between the two circumferential grooves having a width in the range of 5 to 15% of the ground contacting width, wherein the center rib extends continuously in the circumferential direction of the tire. 
     
     
       11. The pneumatic tire according to claim 10, wherein one of the two circumferential grooves is a straight groove, and the other circumferential groove is a zigzag groove. 
     
     
       12. The pneumatic tire according to claim 9, wherein one of the two circumferential grooves is a straight groove, and the other circumferential groove is a zigzag groove.